الفهرس 
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Abstract
Delirium is the most common form of acute brain dysfunction in the post-surgical period since it is associated with poor outcomes and long-term consequences (increased morbidity and mortality, longer hospital stay and increased costs). New diagnostic, preventive and management strategies have helped reduce the incidence of PD and POCD. Identifying those patients most at risk and preventing the development of PD is the most effective way to reduce its incidence. Reducing neuroactive drug doses is especially important for reducing the incidence, duration and severity of delirium episodes. POCD is a major clinical problem of uncertain pathogenesis. It is especially common in elderly patients during the first postoperative week and up to three months after surgery. POCD may temporarily or permanently affect patients’ ability to cope with everyday tasks and is associated with increased mortality. The prevalence of POCD is likely to increase in the future. A preoperative anaesthetic assessment of patients at risk for POCD should include information about the condition and its mostly transient nature. If symptoms of POCD persist after the first 3 months, in our opinion the patient should be referred for appropriate neurocognitive testing even if no preoperative tests were conducted. As to the conduct of general anesthesia, there is some evidence that volatile anaesthetics may be superior to intravenous agents, but current data is insufficient to allow general recommendations. Future research must address both the prevention and treatment of POCD. In all anaesthetic research, measures of postoperative cognition
Our memories are the building blocks of our thinking and learning. They are the framework for our very existence holding the
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pieces of lives. What we remember and what we know defines who we are. Knowing and remembering allows one to understand. The ability to recall and manipulate, shuffle, reorganize, and recreate, is higher order thinking. Memory is a highly complex multifaceted system involving many areas and functions of the brain working together. Our memories are formed through a series of stages. The way memories are made; stored, recalled, and processed is the foundation of cognition. It is our memories that create the highly sophisticated way we are able to relate to our environment, the global community; a long way from eat or be eaten. We continue to evolve. A memory is made in stages; sensory, immediate, short term, working and long-term memory. Memories begin as a deluge of experiences streaming in through our senses. Our sensory memory screens this plethora of sensory stimuli. In a millisecond, this information is sifted by its importance, related to survival, at the brain stem in the RAS (reticular activation system) and thalamus. Emotions strengthen memories and increase their importance. Fear and anxiety cause a reflexive response that inhibits cognitive functioning when hormones are released.
Although the mechanism of delirium has not been elucidated, there has been a significant description of associated patient risk factors. According to the Inouye model some of these may be considered pre-existing; that is, to patient vulnerability and to other precipitating factors, potentially modifiable. The most significant risk factor for POD is dementia and cognitive impairment. Low cognitive and brain reserve may imply greater vulnerability to delirium. Other predisposing risk factors include sensory impairment (vision and hearing), severe illness (American Society of Anaesthesiologists classification >3), dehydration, malnutrition and alcohol abuse
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Vascular risk factors such as age, tobacco use, and the need for vascular surgery were independently associated with postoperative delirium.
The aetiology of postoperative cognitive dysfunction is considered multifactorial, in which there have been implicated many variables including the following: anaesthetic regimen used, postoperative analgesia protocol, the admission in a hospital, level of surgical invasiveness, response-mediated inflammatory cytokines, sleep disturbance and consequent reduction of neurotransmitters such as acetylcholine and adenosine (which in turn produces hyperalgesia) and hypoperfusion and/or intraoperative hypoxia. The only risk factors independently demonstrated, however, include advanced age, previous physical and cognitive impairment, and low educational level .There is a relationship between PD and the subsequent development of short-term POCD.The impact of delirium in long-term dysfunction, however, remains under investigation.
In summary, POCD is highly prevalent up to 3 months postoperatively, especially in elderly patients. There is some evidence that POCD can persist and become a permanent disorder Unfortunately, data about the prevalence of POCD after 3 months is scarce. The ISPOCD investigators examined a subgroup of patients 1–2 years after the initial study and found that 10% satisfied diagnostic criteria for POCD, but this incidence did not differ significantly from a control group.
Preventive measures can be divided into two main groups: multimodal and pharmacological. The first group, the multimodal approach, is based on preventing both vulnerability and precipitating factors, as well for delirium is a multifactorial syndrome. In 2010 the
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English National Clinical Guideline Centre (NCGC) issued guidelines that revised the most significant studies concerning the efficacy of a multimodal approach. Inouye et al. established a multi-component intervention called the Hospital Elder Life Program (HELP). They found their strategy resulted in a significant reduction in the number and duration of episodes of delirium in hospitalised patients. This programme had been successfully reproduced in medical and surgical wards with the same results. Even in elderly patients, it has proven to be an effective measure.
The drug most commonly used, and studied, for treatment of delirium is haloperidol. It is recommended as the drug of choice for the treatment of ICU delirium by the SCCM (Society of Critical Care Medicine) and the APA (American Psychiatric Association) Common doses for ICU patients range from 4 to 20 mg/day. Atypical antipsychotics may also be helpful for delirium treatment
One of the rare variables of cognitive dysfunctions is post cardiac arrest or what is named near death experience. Although traditionally most studies of cardiac arrest have focused on prevention and acute medical treatment, in recent years a number of studies have also focused both on the study of cognitive function during resuscitation, as well as the long term psychological outcome of surviving cardiac arrest. This is an intriguing aspect of the study of cardiopulmonary resuscitation with clinical relevance for all who work within the resuscitation and critical care field. Much of the work in the study of cognitive function during cardiac arrest has evolved from the finding that a proportion of cardiac arrest survivors report thought processes, reasoning and memory formation together with the ability to recall specific details from their resuscitation that are
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consistent with the previously reported near death experiences. Many other studies have also indicated that survival from cardiac arrest leads to specific long term psychological and cognitive changes which include impaired concentration levels and memory function as well as post-traumatic stress disorder.
This essay contain:
cognitive functions
Anatomical and physiological considerations
Postoperative cognitive dysfunction
Near death experience